1. Field of the Invention
The present invention relates to a molded case circuit breaker, and particularly, to a molded case circuit breaker having an instantaneous trip mechanism.
2. Background of the Invention
In general, a molded case circuit breaker is an electrical device for protecting electric loads and an electrical circuit by tripping (breaking) circuits upon occurrence of fault currents, such as, an overcurrent or a short-circuit current.
Among such molded case circuit breaker, a current limitable molded case circuit breaker was introduced in which a direction of a current flowing in a stationary contactor is opposite to a direction of a current flowing in a movable contactor. The current limitable molded case circuit breaker typically uses a stationary contactor with a structure that a conductor extending from an externally exposed terminal into the molded case circuit breaker is then bent towards the terminal, namely, having a shape, like an alphabet “U” being laid. In the current limitable molded case circuit breaker, since the direction of the current flowing in the stationary contactor is opposite to the direction of the current flowing in the movable contactor, when a large fault current such as a short-circuit current flows, an electromagnetic repulsive force is generated between the stationary contactor and the movable contactor, and responsively, the movable contactor is automatically rotated to be separated from the stationary contactor. This operation is called as a current limiting operation, and a molded case circuit breaker having such current limiting function is referred to as a current limitable molded case circuit breaker. In a configuration of a molded case circuit breaker, before operating a trip mechanism, which triggers a switching mechanism to a trip position (i.e. circuit breaking position) in response to detection of a fault current, the current limiting function can immediately break a circuit upon occurrence of the large fault current, so it plays an important role.
On the other hand, a typical molded case circuit breaker is configured such that a direction of a current flowing in a stationary contactor matched with a direction of a current flowing in a movable contactor. The typical molded case circuit breaker generally uses a straight stationary contactor, namely, having a shape, like an alphabet “I” being laid. Since such typical molded case circuit breaker does not have the current limiting function, it should be separately provided with an instantaneous trip mechanism, which operates to trigger the switching mechanism to the trip position as soon as generation of a large fault current, such as a short-circuit current, before a trip mechanism detects the large fault current and triggers the switching mechanism to the trip position.
The present invention relates to the typical molded case circuit breaker having the instantaneous trip mechanism.
The typical molded case circuit breaker according to the related art is configured to perform multi-level operations including detecting a current on a circuit by means of a current transformer, deciding generation of a fault current and outputting a trip signal by means of an overcurrent relay corresponding to a controller, operating a trip actuator responsive to the trip signal, and triggering a switching mechanism to perform a trip operation by releasing a latch in response to the operation of the trip actuator. Thus, the typical molded case circuit breaker according to the related art has problems that a large current, such as a short-circuit current, cannot be instantaneously blocked and a time delay is caused accordingly.
Furthermore, the typical molded case circuit breaker according to the related art has problems of a time delay and a risk of mis-operation upon an electrical signal generation and transfer, a signal processing, an electrical operation responsive to a control signal, such as several steps of detecting a current on a circuit by means of a circuit device, such as a current transformer, transferring a current detect signal via a signal line, processing the signal according to a program by a microprocessor within the over current relay, deciding generation of a fault current, outputting a trip signal to transfer to a trip actuator and driving the trip actuator.